I've been a professor for over 30 years, and I have to tell you that, whether they say it or not, this is the normal way of grading in pretty much every class. If you get a B, it is because some people did better than you did, and some did worse. Over time, we get a sense of what a B looks like, but it still depends on how everyone else did. No professor can get away with giving everyone As or everyone Fs in a class, so this doesn't really change your grade at all (and I've rarely given as many as 15% As, so this isn't lower than usual). This is really no different than what happens in every class, except that the professor said it out loud. It is NEVER the case that each student is graded "individually"; this only makes sense in comparison to other students. I wouldn't get so upset about it.
If you want to speak to the professor's boss, it would probably be his department chair. However, while you can talk with him/her about changes to the syllabus, if the syllabus didn't describe the grading approach at all, you don't have much to complain about.